Those are general tactics for killing any character. He’s not impossible to kill like Alani after initial release. He’s on par with most other characters as far as health/shields.
But that’s part of the problem, it’s his average survival and speed combined with huge damage potential and massive splash attack. It pushes him way over the top.
A bad Ernest player still has presence that affects the outcomes of the game. It’s far too easy to hit with his basic attack considering all you have to do is get it close or bounce it in front of them to do around 150 damage. It wipes minions with a single clip and makes shreds of popcorn characters.
Average Ernest players will tip any otherwise average game single handed. Forcing players back and back and back, until he can get at a sentry, or just sitting back in meltdown and clearing a lane. Yes, I know Toby can do this too. But run a private game sometime. See who does it quicker and punishes nearby Battleborn the most. Simply by proximity to what he’s attacking. No single character should be able to do this just by being that character. It throws balance completely out the window.
Good Ernest players are the worst. I’d rather face a good ambra/galilea combo than a well supported Ernest who knows what the hell he’s doing. At least with Ambra/Galilea I know where the attacks are coming from. Having situational awareness means nothing when a tiny camo coloured chicken can drop bombs on you from anywhere. And not one at a time like the few skills that can do that, a constant stream of high damage/big splash trigger attacks that can bounce and hit from anywhere. What fun is that to play against?
I know what gearbox was going for with his design, but what came out of it was a support character who only needs to support himself to get a big payoff. He doesn’t need to support his team whatsoever, but when he does the effect is even worse.

Glad someone else sees his incredible badassery.